Carles c



(No Model.)

' G. O. TRAPP.

CHAIR OE SEAT IRON.

Patented July 1,1890

lllllllll IWW A 7 zjze/aaaa 171% UNITED STATES PATENT OFFIC I CABLES O. TRAPP, OF PORT WVASHINGTON, WISCONSIN.

CHAIR OR SEAT IRON.

SPECIFICATION forming part of Letters Patent No. 431,536, dated July 1, 1890.

Anplication filed July 16 1889- To all whom it may concern.-

Be it known that I, CABLES C. TRAPP, residing at Port Washington, in the county of Ozaukee, State of \Visconsin, have invented certain new and useful Improvements in Chair or Seat Irons, of which I do declare the following to be a full, clear, and exact description, reference being had to the accompanying drawings, forming part of this specification. 7

My present invention has relation more particularly to that class of ironssuch as are employed upon office chairs, stools, or the likein which the base of the chair is provided with a screw-threaded bushing adapted to receive a suitable threaded spindle, by which the vertical adjustment of the, chair-seat to suit the convenience of the occupant can be effected. In the construction of this class of chair-irons as at present commonly practiced it is customary to attach to the spiderframe or seat of the chair a screw-threaded spindle that enters the correspondinglythreaded bushing of the base portion of the chair, so that when a vertical adjustment of the chair is desired it can be effected by turning the chair-seat. This construction is objectionable, for the reason that there is constant liability to destroythe proper adjustment of the chair by the accidental turning of the seat, either by the occupant himself or by others during his absence, and for the further reason that the wear upon the threaded portions of the spindle,-incident to the frequent turning of the chair-seat, causes a speedy loosening of the parts, thereby per mitting a sagging or wabbling of the chairseat to occur.

One object of my present invention is to provide an improved construction of chair or seat iron, whereby the free turning of the chair-seat is permitted without elfecting the proper vertical adjustment of the seat.

A further object of my invention is to provide a chair or seat iron of such improved construction that the wear upon the screwthreaded portions of the iron, whereby the adjustment of the seat is effected, will be reduced to a minimum.

A still further object of my invention is to avoid the necessity of threading the main Serial No. 317,668. (No model.)

after described, illustrated in the accompa nying drawings, and particularly pointed out in the claims at the end of this specificatian.

Figure 1 is a view in side elevation of a chair seat and base having my improved iron applied thereto. Fig. 2 is an enlarged view in central vertical section through my improved iron. Fig. 3 is a view in transverse section on line 3 3 of Fig. 2.

My invention is shown as applied to one form of tilting ofiice-chair; but it is obvious that it is equally applicable to irons for connecting the seats and bases of stools and the like.

A designates the seat of a chair, to the under side of which is attached a spider-frame B of ordinary construction, this spider-frame being provided with dependent arms I), to which is pivotally connected, as. at b, the head-piece O of the spindle D. A spring E will serve in well-known manner to control the tilting action of the chair; but as this tilting mechanism forms no part of my pres ent invention it need not be more particularly described.

Instead of forming the spindle D with screw-threads, as has been heretofore the practice, I form this spindle with a plain upper port-ion d, of a size adapted to fit snugly Within the correspondingly-plain upper portion of the bore of the bushing F. This bushing F is provided with the usual sockets f to receive the legs, which constitute the base portion of the chair. Theplain part D of the spindle is formed with the lower reduced portion (1, that fits within a screw H, the upper end of the screw being preferably inclined to form a seat for the correspondinglyinclined shoulder d of thespindle. So, also,

the spindle D is by preference formed at its a lower end with a further reduced portion d that enters the correspondingly-reduced bore h of the screw H, the upper portion of this reduced bore it being, by preference, slightly concave to engage the shoulder 01 of the spindle and form a snug bearing therefor.

In order to retain the spindle D in proper connection with the screw H, the extreme lower end of the spindle is preferably furnished with a threaded portion d, that projects through the screw and is engaged with a set-nut 5. The outer face of the screw II will engage with the correspondingly-threaded lower portion g of the bushing F. The lower end of the screw H is also provided with a suitable hand-wheel H, preferably formed in one piece therewith, whereby the turning of the screw can be effected when the vertical adjustment of the chair-seat is to be had, as will hereinafter more fully appear.

If desired, the spindle D may be provided with a stop or shoulder 6 near its upper portion to limit its downward movement and prevent the passage of the screw H from engagement with the bushing.

From the construction of parts as thus far defined it will be seen that when it is desired to efiect the vertical adjustment of the chairseat it is only necessary to turn the handwheel H of the screw H, thus causing the chair-seat A to be raised or lowered to any desired extent. When the proper adjustment of the chair-seat has been thus effected, it can be maintained at the desired position by means of the suitable set-screw K, thatpasses through a corresponding screw-threaded hole in the side of the bushingF and engages with the screw H, and by preference a portion of the screw is flattened or cut away, as at 7, to

afiord a more secure bearing-point for the end of the set-screw K; hence it will be seen that when the chair-seat hasbeen adjusted to the proper position, and the set-screw K has been turned so as to bear against the flattened face 7 of the screw H the further operation of the screw will be arrested, although plainly the free revolution of the chairseat will be permitted, as the spindle D will be free to turn within the bushing F, the shoulder d and d of the spindle bearing upon the corresponding portions of the screw. As the screw H is thus guarded against rotation during the ordinary movement of the chair, it is obvious that all wear upon its threads and upon the threads of the bushing is avoided, and as the spindle D fits snugly within the plain bore of the upper portion of the bushing it is manifest that the wearbetween these parts will be inappreciable and all danger of the lateral sagging or wabbling of the chairseat will be guarded against. By preference the portion (Z of the spindle is formed of such length that the initial bearing of the spindle Dupon the screw H shall occurat the shoulder d so that as the wear of the parts at this point takes place the shoulder d will gradually be brought to bear upon the u er end of the screw H. It is plain, however, that the details of construction above set out may be varied within wide limits without departing from the spirit of my invention.

By the construction above defined I am enabled not only to accomplish the desired results set forth, but with this construction the parts can be very cheaply made, and when set together for use will afiord a far more efficient and durable means for uniting the base and seat of the chair than would be possible if the spindle were formed with screwthreads thereon from end to end in the usual manner.

Having thus described my invention, what I claim as new, and desire to secure by Letters Patent, is

1. A chair or seat iron comprising the combination,with a threaded bushing, of a spindle set within said bushing and having a plain upper portion, a vertically-adjustable screw also set within said bushing and serving to control the vertical adjustment of said spindle, and a suitable device such, for example, as a set-screw, supplemental to said vertically-adj ustable screwfor checking the movement of the adjusting-screw, and thus determining the adjustment of the spindle, substantially as described.

2. A chair or seat iron comprising the combination, with a threaded bushing, of a spindle having its upper portion plain, a Vertically-adjustable hollow screw provided with a hand-wheel and encircling and sustaining the plain portion of the spindle, and a suitable device such, for example, as a setscrewfor checking the movement of the adjusting-screw, substantially as described.

3. A chair or seat iron comprising the combination, with a bushing, of a spindle and a vertically-adjustable screw within said bushing, said screw being provided with a cutaway or flattened face 7, and a set-screw passing through said bushing for engagement with the flattened portion of the adj listing-screw,

substantially as described.

4. A chair or seat iron comprising the combination, with a bushing having a plain bore in its upper portion and a threaded lower portion, of a spindle having a plain upper portion to fit the smooth-bore portion of the bushing, and a hollow screw to engage the threaded portion of the bushing and to receive the lower portion of the spindle, substantially as described. I

5. A chair or seat iron comprising the combination, with a bushing, of a spindle formed with a plain portion D, having a reduced portion d, and a hollow screw H, wherein said reduced portion d of the spindle fits, said parts being suitably connected together, sub- I stantially as described.

l 6. A chair or seat iron comprising the combination, with a bushing, of a spindle consisting of a plain portion D, having the reduced portions (1', and a hollow screw H, having a threaded portion 01, and the hollow screw H, reduced bore h, and having a hand-wheel H, having the hand-Wheel H and the set-nut 5, 10 substantially as described. substantially as described.

7. A chair or seat iron comprising the combination, with a bushing having an upper CABLES TRAPP' plain portion and a lower threaded portion, Witnesses: of a spindle consisting of the plain upper por-' GEO. P. FISHER, J r., tion and the reduced lower portions and I. B. CARPENTER. 

